The spectral (or eigen) gap of a graph is the absolute difference between the biggest and second biggest eigenvalue of the adjacency matrix. To compare spectral gaps across networks, the fraction can be used.
spectral_gap(g, method = "frac")
A string, either "frac" or "abs"
The spectral gap is bounded between 0 and 1 if
method="frac". The closer
the value to one, the bigger the gap.
# The fractional spectral gap of a threshold graph is usually close to 1 g <- threshold_graph(50, 0.3) spectral_gap(g, method = "frac") #>  0.7891508